G.A. Henty 
Lion of the North 

Set in the seventeenth century, this thrilling historical novel geared for younger audiences follows a young Scot named Malcolm as he joins the effort to thwart Catholic forces in Germany who are seeking to vanquish Protestantism. Under the command of Swedish King Gustavus Adolphus, one of the greatest military commanders of all time, Malcolm truly comes into his own, exhibiting bravery and confidence on the battlefield.